The invention applies more particularly to nickel-cadmium batteries installed on board aeroplanes.
The present invention concerns a battery of storage cells and more particularly, a semi-open storage battery, for example, a nickel-cadmium battery.
Such a battery comprises, generally, several storage cells arranged side by side in a general casing closed by a removable lid. Each storage cell comprises a container provided with two output terminals and a bleed valve for gases liable to be evolved during the electrochemical reaction and connections outside of the containers that electrically connect up either in parallel or in series, as the case may be, the terminals of two adjacent storage cells, or, if need be, the terminals of the storage cells to the outside terminals of the battery.
The lid of the said battery has breather holes enabling, on the one hand, the removal of the gases given off by the storage cells and, on the other hand, a flow of air enabling the cooling of their electrical connections.
Numerous uses of a semi-open or semi-sealed storage cell connected as a battery require a rapid recharge of that battery For this purpose, a method of rapid recharging at a constant current in which the current is cut off only when the battery is in a state of overcharge, that state being accompanied by a large emission of gas and more particularly of hydrogen, is known.
Consequently, the electrical connections between the storage cells are surrounded by a mixture of air and gas which may well be explosive if the proportion of hydrogen is greater than 4%. This is then sufficient for a spark that may be caused accidentally at the level of the electrical connections, for instance, in consequence of an insufficient contact between the metallic parts or of a defective tightening of the nuts, to cause an explosive ignition of the gaseous mixture.
For certain batteries used in mines, the problem has been solved by covering the electrical connections of the storage cells with a liquid or solid insulator. But that solution has the disadvantage of preventing all accessiblity to the connections and hence all necessary checks required for proper maintenance.
An aim of the present invention is to overcome that disadvantage.
The present invention has for an object the provision of a battery comprising several storage cells arranged side by side in a general casing closed by a lid, each storage cell comprising a bleed valve for the gases which it may emit and two terminals connected by outside electrical connections to the terminals of the adjacent storage cells, characterized in that it comprises means for conveying the gases likely to be emitted through valves up to first openings formed in the said lid.
The lid of the casing is provided with second openings which form a part of an air flow circuit for the cooling of the connections between storage cells. These second openings are separated from the means for conveying gases emitted during the electrochemical reaction in the cells, more particularly during the overcharge of the battery.
According to an embodiment which is of particular advantage, the means for conveying the gases comprises an intermediate or dummy lid inserted between the lid of the casing and the storage cells. This dummy lid is perforated directly above the electrical connections, in order to allow the flow of air for their cooling; it also comprises funnels whose first ends lead out into the first openings of the lid and whose second ends are fitted about the outlets of the valves of the storage cells.